The Origin of Friday the 13th
Today is Friday the 13th. Whenever the 13th day of a month falls on a Friday we're treated to various explanations from news sources regarding the origins of people's dread of this date. On TV, in newspapers, and throughout the intertubes, numerous authorities will clarify for you how the combination of Friday and the number 13 came to be feared.
I don't want to be left out, and I actually have done a great deal of research into this situation. I have discovered the truth of the matter and it has nothing to do with the order in which apostles arrived at the "last supper" nor with the date and number of attendees at witches' sabbaths that almost certainly never took place.
I am fully confident of the reason that people worry about this date and base my conclusion upon years of textual analysis of sacred and arcane books across cultures and history, upon direct observation, and upon first-hand interactions. I feel entirely secure in stating the reason that people are concerned over Friday the 13th.
Human beings are prone to believing in really dumb things. When particularly ignorant and/or stupid people need something of which to be afraid, they simply make stuff up. This is the origin of superstition.
When they further attach rituals to these superstitions, we wind up with religions.
Enjoy your unlucky day.